The present invention relates to an apparatus for controlling the operating state of an internal combustion engine, and more particularly to an apparatus for controlling the operating state of an internal combustion engine in which a driving parameter of the internal combustion engine is detected and the operating state of the internal combustion engine is controlled in accordance with this detection output.
As one of the methods for controlling the operating state of an internal combustion engine (hereinafter referred to as an engine for simplicity) in an automobile or the like, there is known a method in which the quantity of the intake air per cycle of the cylinder is detected, and the quantity of the fuel injection of the engine is controlled in accordance with the amount of this intake air. This method is based upon the fact that there is approximately a linear relation between the quantity of the intake air and the absolute pressure P.sub.B A in the intake manifold (air suction pipe). This absolute pressure P.sub.B A is detected by a detecting apparatus such as a pressure sensor or the like. By using this detection output or the combination output of this detection output and another engine driving parameter, the fuel injection time T.sub.i is controlled in response thereto.
In this conventional method, the above-mentioned manifold absolute pressure P.sub.B A has to be the value representative directly of the manifold pressure in the suction process of the engine. However, in the case where P.sub.B A in each cycle is changing smoothly, it is actually possible to control the quantity of the fuel injection accurately by measuring the amount of the intake air in a given cycle by using the value P.sub.B A in the immediate preceding cycle, then injecting the fuel for the fuel injection time T.sub.i corresponding to the amount of the intake air thus obtained during the suction process or before this process.
On the other hand, in the case where the value P.sub.B A suddenly changes, for example, when the throttle is suddenly opened, there is a large difference between the measured value P.sub.B A representative of the present suction process and the measured value P.sub.B A representative of the preceding suction process. Therefore, there is a defect in the prior-art method in that the air fuel ratio is rarefied when the throttle is suddenly opened and it is condensed when the throttle is suddenly closed. To eliminate such a defect there is a method to correct the above-mentioned difference by using a throttle opening angle signal. However, even in this method, it is difficult to obtain a desired performance. The conventional method has also an adverse effect to purification of exhaust gases.
The present invention aims at resolution of such problems encountered in the conventional methods as mentioned above. The object is to provide an apparatus for controlling the operating state of an engine in which, even when the absolute pressure in the intake manifold suddenly changes, a stable driving state of the engine is secured and an excellent driving performance can be obtained, and which contributes to purification of exhaust gas.